Getty/David J. Sams(ELYRIA, Ohio) -- Attorneys for a 486-pound Ohio death row inmate claim that the execution procedure "simply will not work" on their client and will cause him a "torturous and lingering death."

Ronald Post, 53, was sentenced to death in 1985 for the shooting death of Helen Vantz, a desk clerk at a motel in Elyria, Ohio.

"Given his unique physical and mental condition there is a substantial risk that any attempt to execute him will result in serious physical and psychological pain to him, as well as an execution involving a torturous and lingering death," Post's attorneys wrote in federal court papers filed Friday.

Post is scheduled to be executed Jan. 16.

Post's attorneys had Dr. David Lubarsky of Miami, Fla., analyze Post and he wrote a six-page declaration about all of the problems with Post's impending execution.

"Mr. Post is not asking for a stay because he's too obese. Rather, Dr. David Lubarsky reviewed Ronald Post's medical records and Ohio's execution protocol and determined that it simply will not work on Mr. Post," Post's attorneys Joseph Wilhelm and Rachel Troutman wrote in a statement to ABC News.

"If it kills him at all, it could take up to 16 hours," they wrote. "Ohio's statute requires a quick and painless lethal injection, and the potential 200+ needle sticks and up to 16 hours that Dr. Lubarsky predicted is not quick and painless."

When Post entered prison, he weighed about 240 pounds and his weight has increased and fluctuated over the nearly 30 years he has been in prison, according to medical records. At one point, he got his weight down to 320 pounds with a mostly vegetarian diet, but then he put the weight back on and returned to a regular diet, according to the court papers.

Post's attorneys claim that he "has not purposefully set out to gain weight."

"Throughout his years on Ohio's death row, Mr. Post has repeatedly expressed a desire to lose weight," his attorneys wrote.

In 1996, Post began writing letters to request medication to help him lose weight.

In a letter to a doctor at Ohio's Department of Rehabilitation and Correction, Post wrote, "I am severely obese and have battled with weight loss all of my life."

He said that he was prescribed amphetamines to control his size from the ages of 15 to 21. He said that he was able to maintain a weight of around 240 pounds from 1978 to 1983.

"Since my incarceration back in March 1984, I have gained weight and at the present time weigh about (350 lbs.) while I lose some weight and gain it right back," Post wrote. "I am tired of being fat and have been more or less starving myself for months, but can't lose hardly any weight at all."

He told the doctor he did not know how to spell the name of the drug he wanted and said he did not care about any potential side effects.

"Please help me in the fight of obesity and to try to live a normal life. I don't care if the pills make me loose [sic] all my hair, all my teeth or even a limb," he wrote.

A doctor wrote back that "the use of amphetamines for weight loss is not authorized within the correctional setting" and advised Post to "continue to monitor your diet and to exercise whenever possible."

Post's attorneys said that severe leg and knee pain from joint deterioration and a lumbar degenerative disc disorder in his back complicate his efforts to lose weight.

They said that Post used to use a walker to get exercise and used the prison's exercise bike "until it broke under his weight."

Post said he was encouraged not to walk because he is at risk of falling, so he only uses a wheelchair now.

His mental state has also contributed to his inability to lose weight, his attorneys said. Post was diagnosed with major depressive disorder and attempted to commit suicide in 2000 by slitting his wrists and ankles with a blade from a pencil sharpener.

The depression also causes Post "to have difficulty with even getting out of bed," his attorneys said.

The state of Ohio uses lethal injection to carry out a death sentence. Post's attorneys said that his weight, vein access issues, scar tissue and other medical problems create a "substantial likelihood of causing severe complications with attempts at an intravenous execution."

On one occasion, Post's attorneys say it took four different medical technicians 17 needle sticks to draw blood from him due to difficulty locating a vein.

They also believe that the gurney table "will most likely not hold Mr. Post's 486 lb. frame" since most operating room tables are not designed to be used with weight over 350 pounds.

Dan Tierney, a spokesman for Ohio Attorney General Mike DeWine's office, told ABC News that the office could only say, "We have received the filing and we are reviewing it to determine further action."